Tesis sobre el tema "Gastrointestinal system Motility"

Bibliography: leaves 206-251. The motor and sensory interactions between nutrients and proximal gut in humans are not well understood, despite the pivotal importance of these interactions on appetite, absorption and thus, nutrition. In part, this lack of knowledge results from technical difficulties in studying motor function in the human gut. In particular, the inability to continuously measure intraluminal flow with any degree of temporal resolution, has impeded progress in this field. The studies described in this thesis focus on nutrient-gut interactions, and also on the development of novel methodologies aimed at advancing the understanding and interpretation of the relationships between intraluminal pressures and flows.

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system that causes motor, visual, and sensory symptoms. Patients also experience constipation, which is not yet understood, but could involve dysfunction of the enteric nervous system (ENS). Autoimmune targeting of the ENS occurs in other autoimmune diseases that exhibit gastrointestinal (GI) symptoms, and similar mechanisms could lead to GI dysfunction in MS. Here, we characterize GI dysmotility in the experimental autoimmune encephalomyelitis (EAE) model of MS and test whether autoantibodies targeting the ENS are present in the serum of MS patients. Male SJL or B6 mice were induced with EAE by immunization against PLP139-151, MOG35-55, or mouse spinal cord homogenate, and monitored daily for somatic motor symptoms. EAE mice developed GI symptoms consistent with those observed in MS. In vivo motility analysis demonstrated slower whole GI transit, and decreased colonic propulsive motility. EAE mice had faster rates of gastric emptying, with no changes in small intestinal motility. Consistent with these results, ex vivo evaluation of isolated colons demonstrated that EAE mice have slower colonic migrating myoelectric complexes and slow wave contractions. Immunohistochemistry of EAE colons exhibited a significant reduction in GFAP area of ENS ganglia, with no changes in HuD, S100, or neuron numbers. To test whether antibodies in MS bind to ENS structures, we collected serum samples from MS patients with constipation and without constipation, and healthy control patients without constipation. Immunoreactivity was tested using indirect immunofluorescence by applying serum samples to guinea pig ENS tissue. MS serum exhibited significantly higher immunoreactivity against guinea pig ENS than control patients, which was particularly evident in MS patients who did not experience constipation. There was no significant difference in immunoreactivity between MS patients with and without constipation. Targets of human MS and mouse EAE serum include enteric glia and neurons. Taken together, these data validate EAE as a model for constipation in MS, and support the concept that this symptom involves changes within the neuromuscular system of the colon. EAE mice develop symptoms consistent with constipation that affects functional ENS networks and may result in structural or phenotypic changes at the cellular level. Serum immunoreactivity suggests that autoantibodies could play a role in the development of constipation in MS by targeting the ENS itself.

Motility of the small intestine is a result of complex neurochemical and hormonal interactions within the intestine. The net motility (contraction) of the intestine is a balance of the influences from the central nervous system, enteric nervous system and hormonal changes in the body. Recently, the discovery of several peptide neurotransmitters common to the brain and the intestine has stimulated new research into the influence of these novel neurotransmitter candidates on intestinal motility at the level of the enteric (intestinal) nervous system. The present studies examined the contractile actions of three families of peptides, the opioids, tachykinins and motilin. Each of these peptide groups has been localized in the intestine, and suggested to function in the control of intestinal motility. The peptides were administered by intraarterial injection to isolated segments of canine small intestine and the resulting contractile activity measured. The results of these experiments demonstrate that all of these peptides may elicit contractile activity of the intestine in very low doses. These actions were further examined, using pharmacological antagonists, to determine the mechanism of action and the receptor types involved in the contractile actions. The opioid peptide induced responses were found to be mediated by two receptor types, mu and delta, located on the enteric nerve and smooth muscle, respectively. Similarly, the tachykinin induced contractions were also found to be due to actions on two receptor types, SP-P and SP-K, located on the nerve and muscle layers, respectively. These data suggest that the opioids and tachykinins may have multiple functions in the intestine dependent on the site of action and the receptor type involved in the response. Administration of motilin induced long-lasting contractile patterns in the intestine. The results also suggest that the actions of motilin are mediated by intermediate neurons of the enteric plexes which synapse on terminal cholinergic motor neurons.

Irritable bowel syndrome (IBS), majorly characterized by irregular bowel movements and abdominal pain, is one of the most prevalent functional gastrointestinal disorders (FGIDs) in the world. Disturbance of gut microbiota, closely linking with gut dysfunction, has been regarded as one of important pathogenetic factors for IBS. However, gut microbiota-driven mechanism underlying IBS remains unclear, which leads to inefficient and non-specific effects of current microbiota-oriented therapy. In this thesis, function-based microbiota investigation with combination of metagenomic and metabolomic analyses was separately performed in IBS cohort and model to precisely link pathogenic species with disordered GI motor function. A series of microbiota manipulation studies in rodents were conducted to explore bacteria-driven molecular mechanism. Firstly, a pilot study with 'omics' analyses revealed fecal microbial structure significantly varied in IBS patients with disorder GI motility relative to healthy controls (HC). Such changed IBS enterotype was functionally characterized by disturbed metabolism of bile acids (BAs) that are previously proved to regulate GI motor function. It indicates microbiota-driven GI dysmotility relevant to disturbance of BA metabolism in IBS. Secondly, a systematic review with meta-analysis was performed to comprehensively understand existing findings related to BA metabolism and its linkage with IBS. Results showed that abnormal BA excretion, previously reported in at least one IBS subtype, is associated with dysregulation of BA synthesis, marked with abnormalities of circulating indices 7α-hydroxy-4-cholesten-3-one (C4) and fibroblast growth factor 19 (FGF19). However, what's the role of gut microbiota in abnormal BA excretion is undetermined. Thirdly, to explore possible role of gut microbiota in abnormal BA excretion in IBS, BA metabolites and BA-related microbiome were simultaneously analyzed in stools of recruited subjects. Results found that total BA and microbiota-derived BAs were remarkably elevated in a quarter of IBS-D patients (BA+IBS-D) who exhibited more frequent defecation, higher level of serum C4 but lower level of serum FGF19 than those with normal BA excretion (BA-IBS-D). In line with metabolic results, abundances of BA-metabolizing bacteria, particularly Clostridium scindens (C. scindens) simultaneously expressed hdhA and bais that are responsible for BA 7α oxidation and dehydroxylation, were highly enriched in fecal metagenomes of such particular IBS-D population. These findings suggest the increased BA-metabolizing microbiome is associated with the dysregulated host BA synthesis in the subgroup of BA+IBS-D patients. Fourthly, by analyzing metabolites and bacteria related to BA metabolism, a neonatal maternal separation (NMS)-induced IBS-D rat model characterized by accelerated GI motility and excessive BA excretion were found to largely mimic gut microbial BA metabolism in BA+IBS-D patients. Specifically, intraluminal total and secondary BAs were significantly elevated in the large intestinal lumens (cecum, proximal colon and feces) of NMS rats, together with increased abundances of hdhA- and bais-expressing Clostridium species, including C. scindens. Moreover, quantitative polymerase chain reaction (PCR) analysis showed upregulated mRNA expression of cholesterol 7 α-hydroxylase (CYP7A1) whereas downregulated mRNA expression of small heterodimer partner (SHP) in the liver of NMS rats, indicating enhanced hepatic BA synthetic level. These observations based on such IBS-D model suggest the association of excessive BA-metabolizing microbiome and increased hepatic BA synthesis. Fifthly, to further clarify whether excessive BA-metabolizing bacteria contribute to enhanced hepatic BA synthesis and to explore the underlying molecular mechanism, we performed bacterial intervention in pseudo germ-free (GF) or/and specific pathogen free (SPF) mice by transplantation of human fecal microbiota and the signal strain C. scindens. Compared with GF mouse recipients of HC and BA-IBS-D fecal microbiota, BA+IBS-D fecal microbial recipients displayed shorter GI transit and increased subsistence of C. scindens in the cecal contents. In line with higher level of serum C4, taurine-conjugated BA contents and mRNA expressions of BA synthetase CYP7A1 and sterol 12α-hydroxylase (CYP8B1) were significantly elevated in the liver of BA+IBS-D recipients. These findings showed bioactive effects of BA+IBS-D fecal microbiota with enrichment of C. scindens on hepatic BA synthesis. Next, to further confirm the effects of the species C. scindens on host BA synthesis, we individually colonized C. scindens strains (ATCC 37504) to pseudo GF and SPF mice. Results showed both mice models with single strain colonization exhibited accelerated GI transit and higher contents of hepatic total and taurine-conjugated BAs compared with individual vehicles treated with PBS. Combining metabolic changes, the upregulated expressions of hepatic CYP7A1 mRNA in colonized mice indicate that C. scindens substantially promote hepatic BA synthesis in colonized mice. Furthermore, contents of taurine-conjugated BAs, served as natural antagonists of farnesoid X receptor (FXR) that negatively control of new BA synthesis, were elevated in ileal lumens of colonized mice. Expressions of FXR-targeted genes SHP and fibroblast growth factor 15 (FGF15) were consistently reduced in the liver and ileum tissues of colonized mice, respectively. Results suggest that suppression of FXR-mediated feedback signaling is involved in Clostridium-driven hepatic BA oversynthesis, which deserve the further investigation. Collectively, the works of this thesis integrating clinical and animal studies indicate that BA-metabolizing bacteria, particularly C. scindens, enhance hepatic BA synthesis and consequently leads to BA overexcretion. It provides novel bacteria-driven mechanism for enhanced GI motility, and supply a direction in precise microbiota-related pathogenesis and medication for IBS-D population in future.

Nitric oxide, a short-lived free radical and neurotransmitter, is responsible for decreased smooth muscle contractility in vitro. When in excess, NO can cause hypotension and is believed to mediate altered intestinal motility. Not enough evidence is available for morphological changes in gastrointestinal smooth muscle and its correlation with motility disorders caused by Escherichia coli-induced NO production. Male Lewis rats were treated with injections of 10 mg/kg LPS from E. coli with or without 12.5 mg/kg of NOS inhibitor, LNMMA. Eighteen to 24 hours following injection, duodenum, ileum, colon, liver, and spleen were harvested for histological analysis. Urine and fecal analysis assessed functional aspects in control and treatment groups. Muscularis externa measurements revealed significant increase in muscle thickness of LPS + LNMMA injected group compared to control and LPS group. However, the average values in control and LPS group were not significantly different. Fecal consistency was significant in all 3 groups. Mean urinary nitrite in the LPS group was 44 times higher than control and 52 times higher than the inhibitor-treated group.<br>Department of Physiology and Health Science

The role of supraspinal, spinal and peripheral alpha-2 adrenoceptors in the regulation of gastrointestinal motility in mice was investigated using anatomically site specific administration of clonidine and adrenoceptor antagonists. Clonidine produced a dose-dependent inhibition of gastrointestinal transit when given by the i.c.v., i.th., or s.c. routes, and was most potent when given i.c.v. Yohimbine, an alpha-2 adrenoceptor antagonist, but not the alpha-1 antagonist prazosin, antagonized the antitransit effects of clonidine. Yohimbine was most potent in antagonizing i.c.v. clonidine; increased doses of the i.c.v. antagonist were required when the agonist was given s.c. After transection of the spinal cord, i.th. clonidine failed to produce an antitransit effect. Additionally, the i.c.v. potency of clonidine decreased approximately 7-fold in spinally-transected mice. The data suggest that the antitransit effects of clonidine occur through actions at alpha-2 adrenoceptors located at both supraspinal and peripheral sites.

Functional constipation (FC) is a major gastrointestional (GI) disorder which affects about 14% population worldwide. However, due to efficacy and safety concerns, more than 50% FC patients are not completely satisfied with current conventional therapies, thus alternative therapies are needed. A substantial part of FC patients have symptom of slow colonic motility, while therapy targeting a single pathway cannot benefit all of them. In this thesis, we searched for novel FC therapeutics from two distinct sources, both of which can improve colonic motility significantly: (1) MaZiRenWan (MZRW), an herb formula from Traditional Chinese Medicine (TCM); and (2) Spexin (SPX), a newly identified neuropeptide that is deregulated in FC. On the basis of efficacy validation for MZRW by randomized, placebo-controlled clinical studies, we investigated the bioactive compounds and pharmacological actions of MZRW. Firstly, a machine-learning based method, namely MOST, was developed to relate bioactive compounds with their mechanism-of-action targets. MOST demonstrated good performance in 7-fold cross-validation (over 87% accuracy) and temporal validation (over 76% accuracy). In the case laxative effect, MOST predicted that acetylcholinesterase (ACHE) was the mechanism-of-action target of aloe-emodin; in vivo studies validated this prediction. Secondly, we analyzed the bioactive compounds and mechanism-of-actions of MZRW with combination of UPLC-QTOF-MS/MS, clustering analysis, organ bath, and MOST approaches. 97 compounds were identified in MZRW extract, and 35 of them can be found in plasma and feces samples of rats with oral administration of MZRW. Chemical space analysis suggested that these compounds can be classified into component groups, while the corresponding pharmacology can be studied with representative compounds. Emodin, amygdalin, albiflorin, honokiol, and naringin were shown to induce spontaneous contractions of rat colonic smooth muscle in vitro. Biological targets in ACh-, estrogen-, prostaglandin-, cannabinoid-, and purine signaling pathways are able to explain the prokinetic effects of representative compounds and component groups. Pharmacological actions of MZRW are mixture of five classic paradigms. Thirdly, the latest results of three-armed, randomized and controlled clinical study showed that MZRW demonstrated comparable efficacy with the first line drug Senna, the first line drug for constipation in HK, during treatment period, both were better than placebo; and the efficacy was more sustainable in follow-up period when comparing that of Senna and placebo. These data suggested the unique pharmacological profile of MZRW for FC. With pharmacometabolomic analysis, we found that change of oleamide is negatively correlated (pearson r = -0.59, p<0.001) with improvement of Complete Spontaneous Bowel Movement (CSBM) in MZRW group, but not in Senna or placebo group. Oleamide is up-regulated in FC patients compared with healthy controls, and MZRW can significantly reduce oleamide in FC patients (n=30), healthy human volunteers (n=23), and in normal mice (n=12) serum, ileum, and colon. The regulation of oleamide by MZRW is possibly via augmenting FAAH-mediated degradation. Lastly, we investigated the possibility to use SPX, the newly identified, FC-associated neuropeptide to change GI motility. The deregulation of SPX has been found in several disorders including FC, however, the metabolic instability of SPX prevent it to be directly used in clinical practices. Our investigation through combination of molecular dynamics (MD) simulations and NMR analysis suggested a β-turn-helix-β-turn (βαβ) conformation for human spexin (hSPX) adopts in solution. Consistent with this conformation, cyclic analogues of hSPX with a disulfide bond between residue 1 and 13, LH101 (CWTPQAMLYLKGCQ-NH2), activated both GalR2 (EC50=1.19 μM) and GalR3 (EC50=1.56 μM) with potency comparable to wild type, and that the acetylation at the N-terminal, LH101(Ac) raises the potency EC50=0.38 μM on GalR2 and EC50=0.39 μM on GalR3. The serum half lives of LH101 (t1/2=355.7 min) and LH101(Ac) (t1/2=1973.7 min) were significantly longer than the wild type (t1/2=66.5 min), and LH101(Ac) induces the contractions of mice intestinal segment in vitro and attenuates the oleamide-induced slow GI motility in vivo. Collectively, our studies in MZRW suggested that estrogen and oleamide signaling pathways are potential new targets to develop novel therapeutics for FC, while lead compounds targeting these pathways could be found from MZRW. The final study suggested CSAs have potential to be developed as new FC therapy by targeting the galanin receptor associated pathway.

A isquemia aguda mesentérica é uma condição de grande emergência vascular, que é fatal na população mundial em 60% a 80% dos casos. O objetivo desse trabalho foi estudar, os efeitos da isquemia/reperfusão intestinal sobre o receptor P2X2 e diferentes classes neuronais no plexo mioentérico. Foram analisados o íleo de ratos: controle, Sham e isquemia/reperfusão intestinal (I/R-i) com de 24h e 1 semana de reperfusão. Foram realizadas colocalização do receptor P2X2 com a NOS, ChAT, Calb, Calr, S100 e anti-HuC/D. Os resultados mostraram diminuição de neurônios P2X2-ir colocalizados com a NOS, ChAT e Hu, e um aumento com S100 no grupo I/R-i 1 semana. A densidade apresentou um aumento de células P2X2-ir e S100 e diminuição de ChAT e Hu no grupo I/R-i de 1 semana. O perfil neuronal apresentou um aumento nos neurônios NOS-ir, ChAT, Calb (Dogiel Tipo II) e Calr. Conclui-se que a isquemia levou a alterações diferenciadas no receptor P2X2, células gliais e neurônios entéricos, que podem causar disfunções gastrintestinais, como por exemplo, problemas na motilidade intestinal.<br>The acute mesenteric ischemia is a vascular condition of extreme emergency, which is fatal in the world population by 60% to 80% of cases. The aim of this work was to study the effects of intestinal ischemia/reperfusion on the P2X2 receptor and different neuronal classes in the myenteric plexus. We analyzed the ileum of rats: control, Sham and ischemia/reperfusion (I/R-i) with 24 hours and 1 week of reperfusion. The colocalization were performed by P2X2 receptor with NOS, ChAT, Calb, Calr, S100 and anti-HUC/D. The results showed a decrease of P2X2-ir neurons colocalizated with ChAT and Hu, and an increase in the group with S100 in the I/R-i 1 week group. The density of cells showed an increase of P2X2-ir and S100 and a decrease of Hu and ChAT in I/R-i 1 week group. The profile area showed an increase in NOS-ir, ChAT-ir, Calb (Dogiel Type II) and Calr-ir neurons. We conclude that ischemia led to different changes in P2X2 receptor, enteric neurons and glial cells, which can cause gastrointestinal disorders, such as intestinal motility disorder.

In response to ingestion of nutrients, enteroendocrine L cells secrete the incretin hormone, glucagon-like peptide-1 (GLP-1), to enhance glucose-dependent insulin release. Therapies related to GLP-1 are approved for type 2 diabetes. The GLP-1 receptor (GLP-1R) is expressed in cells of the gastrointestinal tract and elsewhere. In pancreatic beta cells, GLP-1R are coupled to the Gs/cAMP/PKA pathway. The expression and function of GLP-1R in gastrointestinal smooth muscle are not known. Aim. To test the hypothesis that GLP-1 regulates smooth muscle function by acting on GLP-1R expressed on smooth muscle. Methods. Smooth muscle cells (SMC) were isolated and cultured. Expression of GLP-1R mRNA was measured by RT-PCR. Expression of GLP-1R protein was measured by western blot. The effect of GLP-1 (7-36) amide on Gαs activation, cAMP formation, and PKA activity was examined in cultured SMC. The effect of GLP-1 on basal activity and on acetylcholine-induced contraction was measured in intact colon via organ bath. Results. Amplification of GLP-1R mRNA suggested expression of GLP-1R mRNA in mucosal and non-mucosal colon cells, which was confirmed in pure SMC cultures. Similar patterns of protein expression were obtained with western blot. Addition of GLP-1 caused relaxation of phasic activity and agonist-induced tonic contractions in intact colon, suggesting a role of smooth muscle Gs-coupled GLP-1R in mediating relaxation. In SMC, GLP-1 (7-36) amide activated Gas, increased cAMP levels, and stimulated PKA activity. Conclusion. Colonic SMC express GLP-1R, and GLP-1 inhibits both basal and acetylcholine-induced contraction. The GLP1-R is coupled to the heterotrimeric G protein, Gas.

Admite-se que mais de 40% das crianças são acometidas pela desnutrição crônica em Moçambique (África Oriental). A doença pode estar relacionada, entre outros fatores, à qualidade da dieta que é oferecida à população, já que é bastante precária, pois exibe sérias deficiências de ferro, gordura e, principalmente, proteína animal em sua composição. Essa insuficiência proteica poderia acarretar em prejuízo ao desenvolvimento do organismo, pois a proteína animal é considerada uma boa fonte de aminoácidos essenciais, em decorrência de sua maior digestibilidade e absorção no intestino delgado, quando comparadas às fontes de origem vegetal. Na presente pesquisa foi reproduzida em laboratório, a dieta básica da população de Moçambique (DM), com o objetivo de avaliar seus efeitos nos componentes do plexo mioentérico e na mucosa dos segmentos do intestino delgado de ratos Wistar. Para isso, os animais foram divididos nos grupos Controle, com dieta AIN-93G com adição de 20% de caseína (NN21 e NN42); Dieta de Moçambique (DM21 e DM42) e Dieta Moçambique suplementada, acrescida de 20% de caseína (NM21 e NM42); e grupo Renutrido (RM42), composto por animais do grupo DM21 que, a partir do 22º dia, receberam a dieta NM até atingirem 42 dias de vida. Os segmentos foram coletados e submetidos às técnicas histoquímicas da NADH-diaforase e da NADPH-diaforase para evidenciação de neurônios do plexo mioentérico; histológicas (HE, Picro-sírius, Weigert) para avaliação da parede intestinal, mucosa, gânglios e seu tecido conjuntivo associado; de microscopia eletrônica de varredura (MEV) para observação da estrutura da mucosa; e de microscopia eletrônica de transmissão (MET) para a ultraestrutura dos componentes ganglionares. Estatisticamente, o peso corporal e o comprimento dos animais submetidos à dieta de Moçambique estavam abaixo dos valores encontrados para os animais controle. Na análise qualitativa, observou-se a presença de fibras elásticas, elaunínicas e oxitalânicas, assim como predominância de fibras colágenas do tipo I nos grupos NN42 e DM42, e do tipo III nos grupos NM42 e RM42 ao redor dos gânglios. A mucosa apresentou uma menor área no grupo DM21 com recuperação em DM42, com diminuição da altura das vilosidades nos dois grupos. Foram observadas alterações na organização do retículo endoplasmático rugoso e disposição dos materiais fibrilares e granulares do nucléolo dos animais DM. Sob MEV as vilosidades do grupo DM42 apresentaram superfície mais lisa, com poucas delimitações entre elas. A densidade dos neurônios reativos à NADH diminuiu de 21 para 42 dias em todos os grupos; porém, o DM21 e DM42 apresentou uma maior densidade. Os neurônios reativos à NADPH apresentaram a diminuição da densidade de 21 para 42 dias nos grupos DM e NM, quando comparados ao controle. Assim, conclui-se que a dieta vegetal de Moçambique levou à alterações na morfologia da mucosa, parede intestinal e neurônios entéricos, como uma forma de adaptação à dieta imposta<br>It is assumed that more than 40% of children are affected by chronic malnutrition in Mozambique (East Africa). The disease may be related, among other factors, the quality of diet that is offered to the population, since it is quite precarious, because it displays serious deficiencies of iron, fat and especially animal protein in their composition. This protein failure could result in damage to the development of the organism, as animal protein is considered a good source of essential amino acids, due to its higher digestibility and absorption in the small intestine when compared to vegetable sources. In this research has been reproduced in the laboratory, the staple diet of the population of Mozambique (DM), in order to evaluate its effects on components of the myenteric plexus and the mucosa of the small intestine segments of Wistar rats. For this, the animals were divided into control groups with AIN-93G diet with the addition of 20% casein (NN21 and NN42); Diet Mozambique (DM21 and DM42) and diet supplemented Mozambique, plus 20% casein (NM21 and NM42); and Refeeding group (RM42), consisting of the animals DM21 group, from the 22th day, given NM diet until they reached 42 days of life. The segments were collected and submitted to histochemical techniques of NADH-diaphorase and NADPH-diaphorase for disclosure of neurons of the myenteric plexus; histologic (HE, Sirius red, Weigert) for evaluation of the intestinal wall, mucosa, lymph nodes and its associated connective tissue; scanning electron microscopy (SEM) for observation of mucosal structure; and Transmission electron microscopy (TEM) ultrastructure to ganglion components. Statistically, body weight and length of the animals submitted to Mozambique diet were below the values found for control animals. Qualitative analysis showed the presence of elastic fibers, and elauninic oxytalan, and predominance of type I collagen fibers in the NN42 and DM42 groups, and type III in the NM42 and RM42 groups around the ganglia. The mucosa showed a smaller area in DM21 group recovery DM42, with a decrease in villus height in both groups. There have been changes in the organization of the rough endoplasmic reticulum and arrangement of fibrillar and granular materials nucleolus of DM animals. Under SEM the villi of the DM42 group showed smoother surface, with few boundaries between them. The density of reactive NADH decreased from 21 to 42 days in all groups; however, the DM21 and DM42 had a higher density. Reactive neurons to NADPH had decreased from 21 to 42 days density in DM and NM groups when compared to the control. Thus, it is concluded that vegetable diet Mozambique led to changes in the morphology of the mucosa, the intestinal wall and enteric neurons, as a way to adapt to the imposed diet

More than 1.2 million people are estimated to be currently living with the human immunodeficiency virus (HIV) in the United States of America. The gastrointestinal (GI) tract is both a major target and an important component of HIV pathogenesis. The GI processes that are dysregulated during HIV infection are controlled by the enteric nervous system (ENS). Indeed, both clinical and experimental studies have implicated the ENS in HIV and simian immunodeficiency virus (SIV) pathogenesis. In addition to direct viral effects, the HIV virus also indirectly affects the GI tract via cellular and/or viral toxins released by infected cells. Trans-activator of transcription (Tat) is a viral toxin that plays an important role in replication of the HIV virus. While, the HIV virus does not directly infect neurons, Tat has been shown to modulate neuronal function. HIV infection in the gut is accompanied by: translocation of bacteria and bacterial products from the gut lumen to peripheral blood, immune activation and inflammation. Lipopolysaccharide (LPS) is a major bacterial product that is used to determine the rate of bacterial translocation and to drive inflammation. Despite reports of enteric ganglionitis in SIV infected monkeys and autonomic denervation in the jejunum of HIV patients, little is known of the mechanism underlying enteric neuropathogenesis in HIV and the role of the ENS in HIV pathogenesis. In the present study, we assessed the effects of Tat on enteric neuronal excitability and how Tat and LPS interact in the ENS to bring about inflammation and GI motility problems observed in HIV patients. We show that Tat significantly increased enteric neuronal excitability by modulating sodium channels expressed on enteric neurons. Tat sensitized ENS cells to LPS-mediated increase in pro-inflammatory cytokines via a TLR4-mediated pathway involving MyD88. Mice expressing the tat transgene (Tat+) had faster GI transit rates and significantly higher frequencies of diameter changes in the proximal ileum than controls (Tat-). Tat+ mice were also more sensitive to LPS-mediated decreases in colonic transit rate. This study highlights the role of viral and bacterial proteins in HIV pathogenesis in the gastrointestinal tract and also demonstrates a critical role of the ENS in HIV pathogenesis.

Dor abdominal pode ser consequente a inúmeras causas, entre as várias possibilidades precisamos ficar atentos aos quadros de isquemia intestinal. No trato digestório a isquemia/reperfusão intestinal (I/R-i) acarreta alterações morfológicas nos neurônios entéricos. Este trabalho tem como objetivo analisar o comportamento das diferentes classes neuronais e do receptor P2X7 no plexo mioentérico do íleo de ratos Wistar submetidos à I/R-i. A isquemia intestinal foi obtida pela obstrução do fluxo sanguíneo das artérias ileais no período de 35 minutos, seguida pelos períodos de reperfusão de 6, 24, 72 horas e 1 semana. No grupo sham não houve a oclusão das artérias ileais. Os tecidos foram preparados por métodos imunohistoquímicos de duplas marcações do receptor P2X7 com a Óxido Nítrico Sintase neuronal (NOSn), calbindina (Calb), calretinina (Calr) e Acetilcolina Transferase (ChAT) e do receptor P2X7, da NOSn e da ChAT com o pan-neuronal anti-HuC/D. As análises qualitativas e quantitativas das contagens das duplas marcações, das densidades neuronais e da área dos perfis foram obtidas dos microscópios de fluorescência e de Confocal de Varredura à Laser. Os resultados qualitativos demonstraram diminuição da expressão do receptor P2X7 no grupo I/R-i de 24 horas e retorno da expressão nos grupos I/R-i de 72 horas e 1 semana. Os dados quantitativos demonstraram: a) os neurônios do plexo mioentérico foram imunorreativos ao receptor P2X7; b) não houve alterações significativas nas duplas marcações do receptor P2X7 com os neurônios NOSn-ir, Calr-ir, Calb-ir e ChAT-ir nos grupos sham e I/R-i; c) não houve alterações significativas nas duplas marcações do receptor P2X7, e dos neurônios NOSn-ir e ChAT-ir com o pan-neuronal anti-HuC/D nos grupos sham e I/R-i; d) houve diminuição nas densidades nos grupos I/R-i com 6, 24, 72 horas e 1 semana dos neurônios P2X7-ir, NOSn-ir, Calr-ir, Calb-ir, ChAT-ir e anti-HuC/D-ir quando comparados aos grupos sham; e) houve um aumento na área do perfil dos neurônios NOSn-ir nos grupos I/R-i de 6 e 24 horas, nos neurônios ChAT-ir houve um aumento no grupo I/R-i de 1 semana e nos neurônios Calr-ir houve uma diminuição no grupo I/R-i de 6 horas e um aumento no grupo I/R-i de 24 horas quando comparados aos grupos sham. O presente estudo demonstrou que a I/R-i está associada com a perda significativa de diferentes subpopulações de neurônios do plexo mioentérico acompanhada por diversas alterações morfológicas, o que pode acarretar problemas na motilidade intestinal.<br>Abdominal pain may be consequent to numerous causes, among the various possibilities need to be attentive to intestinal ischemia. In the digestive tract the intestinal ischemia-reperfusion (I/R-i) causes morphological changes in enteric neurons. The aim of the work was to analyze the behavior of different neurons and P2X7 receptor in the myenteric plexus of the ileum of rats subjected to I/R-i. Intestinal ischemia was obtained by the obstruction of blood flow in the ileal arteries period of 35 minutes followed by reperfusion periods of 6, 24, 72 hours and 1 week. In the sham group there was no occlusion of the ileal arteries. The tissues were prepared by immunohistochemical methods for double staining of P2X7 receptor with neuronal nitric oxide synthase (nNOS), calbindin, calretinin and acetylcholine transferase (ChAT) and P2X7 receptor, the nNOS and ChAT with pan-neuronal marker anti-HuC/D The qualitative and quantitative analysis of the counting of double staining, the neuronal density and the area of the cell body profile were obtained from fluorescence microscopy and confocal scanning laser. The qualitative results showed decreased expression of the P2X7 receptor in I/R-i for 24 hours group and return the expression in I/R-i for 72 hours and 1 week groups. The quantitative data showed: a) neurons in the myenteric plexus were immunoreactive for P2X7 receptor; b) no significant changes in the double staining of P2X7 receptor with nNOS, calretinin, calbindin and ChAT neurons in the sham and I/R-i groups; c) does not significant changes in the double staining of the P2X7 receptor, the nNOS and ChAT neurons with the pan-neuronal marker anti-HuC/D in sham and I/R-i groups; d) the densities of the P2X7 receptor, nNOS-IR, calretinin-IR, calbindin-IR, ChAT-IR and anti-HuC/D-IR neurons were decreased in I/R-i 6, 24, 72 hours and 1 week groups, when compared to sham group; e) the profile area was increased in nNOS-IR neurons in the I/R-i for 6 and 24 hours groups, ChAT-IR neurons in I/R-i 1 week group and in the calretinin-IR neurons there was a decrease in I/R-i 6 hours group and an increase in I/R-i for 24 hours group when compared to sham group. The present study demonstrated that I/R-i is associated with significant loss of different subpopulations of neurons in the myenteric plexus accompanied by several morphological changes, which can cause intestinal motility disorder.

Isovaleric Acid (IVA) is a 5-carbon branched chain fatty acid present in fermented foods and produced by the fermentation of leucine by colonic bacteria. IVA activates G-protein coupled receptors such as FFAR2, FFAR3, and OR51E1 known to be expressed on enteric neurons and enteroendocrine cells. We previously reported that the shorter, straight chain fatty acids acetate, propionate and butyrate, differentially affect colonic propulsion; however, the effect of branched chain fatty acids on gastrointestinal motility is unknown. We hypothesize that IVA relaxes smooth muscle in a cAMP/PKA dependent manner by direct action on smooth muscle cells. IVA will also decrease peristalsis and encourage retention of luminal contents. This thesis investigates the effect of IVA on smooth muscle tension and peristaltic activity in isolated colon and individual smooth muscle cells. Colon segments from C57BL/6J mice were placed in a longitudinal orientation in organ baths in Krebs buffer and fastened to force transducers. Segments were contracted with 10 μM acetylcholine (ACh) and the effects of IVA at several concentrations were measured in the absence and presence of Nitric Oxide Synthase inhibitor L-N-nitroarginine (L-NNA), neuronal action potential inhibitor tetrodotoxin (TTX), and adenylate cyclase inhibitor SQ22536. To study individual live cells, mouse smooth muscle was isolated from colon, suspended in smooth muscle buffer, and after contraction with ACh were relaxed with micromolar concentrations of IVA. For peristalsis studies, whole colonic segments isolated from C57BL/6J were catheterized and placed horizontally in organ baths with circulating Krebs buffer. The colon was clamped on the anal end, and a solution (5 μL per mm of colon length) of either Krebs buffer or 50 mM IVA was delivered from the oral end to the lumen. Video of the peristalsis was then analyzed for diameter, changes in diameter, velocity of diameter changes along the length of the colon, normalized to the anatomical changes in the proximal region. IVA in concentrations of 10 mM to 50 mM relaxed the ACh-induced contraction in a sigmoidal fashion. In separate studies, L-NNA nor TTX affected the ability of IVA to inhibit relaxation. SQ22536 inhibited IVA induced relaxation in longitudinal colon compared to vehicle control. In isolated cells, SQ22536 and PKA inhibitor H-89 inhibited IVA-induced relaxation. In peristalsis studies, 50 mM IVA in Krebs buffer changed the character of the peristaltic action by increasing proximal diameter, inhibiting contractions in the proximal end of the colon, and decreasing overall velocity of peristaltic contractions in the proximal region. The data indicate that the branched chain fatty acid IVA causes a concentration-dependent relaxation of colonic smooth muscle that is direct to the smooth muscle and independent of neuronal activity. This relaxation is cAMP/PKA dependent. In addition to the direct relaxation of smooth muscle, intraluminal IVA decreased overall colonic propulsive activity and encouraged retention of the luminal contents. We conclude that the ingestion and production of branched chain fatty acids could affect overall GI motility and is an area for study in dietary and therapeutic control of bowel activity.

Gastric emptying, and small intestinal glucose exposure and absorption, are potentially important determinants of postprandial blood glucose homeostasis and energy intake. The studies presented in this thesis were designed to provide novel insights into the interrelationships of upper gastrointestinal function with glycaemia and appetite in both health and type 2 diabetes. The issues which were addressed relate in particular to : ( i ) the physiology, regulation and measurement of gastric and small intestinal motility, ( ii ) the relationships between small intestinal glucose exposure, incretin hormone release, antropyloroduodenal motility and appetite, and ( iii ) the impact of gastric and small intestinal motility on glycaemia. The study reported in chapter 4 evaluated the effect of variations in small intestinal glucose delivery on blood glucose, plasma insulin, and incretin hormone ( GLP - 1 and GIP ) concentrations in healthy subjects. While initially rapid, and subsequently slower, duodenal glucose delivery potentiated incretin and insulin responses when compared to constant delivery of an identical glucose load, the overall glycaemic excursion was not improved. These observations add to the rationale for the use of dietary and pharmacological strategies designed to reduce postprandial glycaemic excursions in health and type 2 diabetes by slowing gastric emptying, rather than initially accelerating it. Fat is a potent inhibitor of gastric emptying. In chapter 5, the acute effect of slowing gastric emptying by fat, on postprandial glycaemia in type 2 diabetes, has been evaluated. Ingestion of a small amount of olive oil, as a 'preload' 30 min before a carbohydrate meal, was shown to markedly slow gastric emptying, affect intragastric meal distribution, delay the postprandial rises in blood glucose, plasma insulin, and GIP, and stimulate GLP - 1. In contrast, the effects of including the same amount of oil within the meal, on gastric emptying, as well as glycaemic and incretin responses, were relatively modest. As blood glucose levels had not returned to baseline by 210 min ( the end of each experiment ), effects on the overall glycaemic ( or insulinaemic ) response could not be determined ; this represents a priority for future studies. The energy content of a meal is a major determinant of its rate of gastric emptying. The study reported in chapter 6 demonstrated that the substitution of an artificial sweetener ( "diet" mixer ) for sucrose ( "regular" mixer ) in a mixed alcoholic beverage has a major impact on the rate of gastric emptying and alcohol absorption in healthy adults. A low calorie alcohol - containing drink ( made with "diet" mixer ) emptied from the stomach much more rapidly and resulted in higher blood alcohol concentrations when compared with a relatively high calorie alcoholic drink ( made with "regular" mixer ). These observations highlight the need for community awareness of factors, other than the alcohol content of a beverage, which should be taken into account in considering safe levels of consumption and the potential for inebriation. Upper gastrointestinal motor function and incretin hormone ( GLP - 1 and GIP ) secretion are known to be major determinants of postprandial glycaemia and insulinaemia, however, the impact of small intestinal flow events on glucose absorption and incretin release has not been evaluated. In the study reported in chapter 7, intraduodenal pressures and impedance signals were recorded simultaneously in healthy humans, while glucose was infused into the duodenum in the presence and absence of the anticholinergic drug, hyoscine butylbromide. The frequency of duodenal flow events ( evaluated by impedance ) was suppressed by hyoscine much more than that of duodenal pressure waves, or propagated pressure wave sequences ( evaluated by manometry ). Blood glucose and plasma 3 - OMG concentrations ( the latter provide an index of glucose absorption ) were lower during hyoscine than saline. Plasma insulin, GLP - 1, and GIP concentrations were initially lower during hyoscine. The disparity between impedance measurements and manometry in detecting alterations in flow during hyoscine infusion was marked and, accordingly, supports the potential utility of small intestinal impedance monitoring to evaluate alterations in gastrointestinal transit in various disease states. The observations also indicate that the frequency of small intestinal flow events is a determinant of both glucose absorption and incretin release. Intraduodenal administration of the local anaesthetic, benzocaine, has been shown to attenuate the release of cholecystokinin ( CCK ) by small intestinal lipid, and the perceptions of fullness, discomfort, and nausea induced by gastric distension during small intestinal lipid infusion, implying that local neural mechanisms may regulate CCK release in response to intraduodenal nutrients. In chapter 8, the effects of intraduodenal administration of benzocaine on : ( i ) blood glucose, incretin hormone and insulin concentrations ( ii ) antropyloroduodenal motility, and ( iii ) gut sensations and appetite, in response to an intraduodenal glucose infusion, were evaluated in healthy subjects. Benzocaine attenuated the perceptions of abdominal bloating and nausea, but had no effect on antro - pyloro duodenal motility, blood glucose concentrations, or incretin responses. These observations indicate that the induction of sensations by small intestinal glucose is mediated by local neural pathways. GLP - 1 is released from L - cells whose density is greatest in the distal jejunum and ileum, GIP predominantly from duodenal K cells, and cholecystokinin ( CCK ) from I cells, which appear confined to the duodenum and jejunum. The study reported in chapter 9 evaluated the effects of infusion of glucose into different gut regions ( mid - jejunal vs duodenal ) on incretin hormones, CCK, appetite and energy intake in healthy subjects. There was no difference in the incretin responses between infusion at the two sites ( 85 cm apart ), however the stimulation of CCK and suppression of hunger and energy intake, were greater with the duodenal compared to the jejunal infusion. These observations indicate that the site of small intestinal glucose exposure is a determinant of CCK release and appetite. Both glucose and fat are known to be potent stimuli for incretin secretion, but the effect of protein is uncertain. Protein may also stimulate insulin secretion directly via absorption of amino acids. In the study reported in chapter 10, gastric emptying, and the blood glucose, insulin and incretin responses, alter a 300 mL drink containing 50 g glucose, 25 g protein, or both 50 g glucose and 25 g protein, were evaluated in healthy subjects. This study established that the addition of protein to an oral glucose load improved the glycaemic response, predominantly by slowing gastric emptying. However, protein also stimulated incretin and insulin secretion. These observations have implications for the use of protein in the dietary management of type 2 diabetes. The relationship between glycaemia, incretin hormones, appetite suppression and modulation of antropyloroduodenal motility with duodenal glucose delivery is poorly defined. In chapter 11, the effects of intraduodenal glucose infusions at different caloric rates ( of 1 kcal / min, 2 kcal / min and 4 kcal / min, or control ( saline ) ) on antropyloroduodenal motility, plasma GLP - 1, GIP and CCK, appetite and energy intake have been evaluated in healthy subjects. While there was a rise in blood glucose in response to all the intraduodenal glucose loads, there was no significant difference in the response to infusions at 2 kcal / min and 4 kcal / min. An initial, transient, small rise in GLP - 1 was evident, in response to all glucose loads, but a sustained and progressive rise only occurred with the 4 kcal / min infusion. In contrast, a load - dependent stimulation of GIP occurred in response to all glucose infusions. The stimulation of CCK was much greater in response to the 4 kcal / min infusion. While antral pressures were suppressed by all rates of glucose infusion, the stimulation of basal pyloric pressure was load - dependent. Energy intake was suppressed only by the 4 kcal / min infusion. This may potentially reflect the substantially greater stimulation of CCK, consistent with the observations reported in chapter 9. This study establishes that there is a substantial discordance in the acute effects of small intestinal glucose on glycaemia, incretin hormones, CCK, motility and appetite. It is planned to perform measurements of plasma insulin on the stored samples - these results were, unfortunately, not available at the time of the submission of this thesis and are critical to the overall interpretation of the data.<br>Thesis (Ph.D.)--University of Adelaide, School of Medicine, Discipline of Medicine, 2007.

Bibliography: leaves 206-251.<br>xii, 251 leaves : ill. ; 30 cm.<br>Title page, contents and abstract only. The complete thesis in print form is available from the University Library.<br>The motor and sensory interactions between nutrients and proximal gut in humans are not well understood, despite the pivotal importance of these interactions on appetite, absorption and thus, nutrition. In part, this lack of knowledge results from technical difficulties in studying motor function in the human gut. In particular, the inability to continuously measure intraluminal flow with any degree of temporal resolution, has impeded progress in this field. The studies described in this thesis focus on nutrient-gut interactions, and also on the development of novel methodologies aimed at advancing the understanding and interpretation of the relationships between intraluminal pressures and flows.<br>Thesis (Ph.D.)--University of Adelaide, Dept. of Medicine, 2000

Includes bibliographical references (leaves 349-440).<br>440 leaves : ill. ; 30 cm.<br>The broad areas addressed are: the effect of physiological changes in the blood glucose concentration in the regulation of gastroduodenal motor and sensory function; the effect of acute hyperglycaemia on gastric motor and sensory function in patients with diabetes mellitus and the motor response to prokinetic therapy; the relationships between small intestinal nutrient exposure, gastrointestinal peptide hormone release, antropyloric motility and appetite; and, the effect of aging on the proximal gastric response to distension and food intake.<br>Thesis (Ph.D.)--Adelaide University, Dept. of Medicine, 2001

Includes bibliographical references (leaves 349-440).<br>440 leaves : ill. ; 30 cm.<br>Title page, contents and abstract only. The complete thesis in print form is available from the University Library.<br>The broad areas addressed are: the effect of physiological changes in the blood glucose concentration in the regulation of gastroduodenal motor and sensory function; the effect of acute hyperglycaemia on gastric motor and sensory function in patients with diabetes mellitus and the motor response to prokinetic therapy; the relationships between small intestinal nutrient exposure, gastrointestinal peptide hormone release, antropyloric motility and appetite; and, the effect of aging on the proximal gastric response to distension and food intake.<br>Thesis (Ph.D.)--Adelaide University, Dept. of Medicine, 2001

Inadequate delivery of nutrition to the critically ill is common, and may adversely affect clinical outcomes, including survival. This thesis reports studies designed to characterise the gastrointestinal dysfunction underlying feed intolerance in the critically ill, as well as the pathophysiology of these dysfunctions, and investigate potential therapeutic measures. While it has been established that enteral nutrition is frequently unsuccessful in the critically ill, assessment of the success of feeding in an Australian intensive care unit (ICU) had not been performed previously. A prospective survey examined the incidence of, and risk factors for, feed intolerance in the ICU at the Royal Adelaide Hospital and demonstrated that, in 40 patients receiving enteral feeding, only about 60% of their nutritional requirements were met at the end of the first week. The main cause for this lack of success was large gastric residual volumes, indicative of delayed gastric emptying (GE). This study, accordingly, quantified the limitations of nutritional delivery in contemporary practice in a local ICU. The results suggest that a better understanding of the pathogenesis underlying this problem is warranted in order to direct research into improved therapies. Scintigraphy is the most accurate technique to measure GE, but is difficult to perform in the ICU. A simpler, more convenient, test would increase the accessibility of GE measurement for both research and clinical purposes. A study comparing a breath test technique and gastric residual volume measurement to the scintigraphic measurement of GE in 25 mechanically ventilated patients demonstrated that GE measured by a breath test technique closely correlated with that measured by scintigraphy. While the breath test had a specificity of 100% it only had a sensitivity of about 60% in the prediction of delayed GE. Similarly, gastric residual volume measurement correlated with scintigraphic measurement of GE but also lacked sensitivity. The breath test has previously been demonstrated to be highly reproducible and it represents a useful option for repeated measurement of GE in the same patient. It is therefore likely to be useful to determine changes in GE over time or in response to a therapeutic intervention. There is a lack of information about the prevalence and determinants of delayed GE in the critically ill. Previous studies have substantial limitations and scintigraphic measurement of GE has only rarely been used. A study comparing GE measured by scintigraphy in 25 patients to 14 healthy subjects demonstrated that GE was delayed in approximately 50% of the ICU patients (>10% retention at 4h) and markedly delayed in about 20% (>50% retention at 4h). Patients with trauma and sepsis appeared to have a relatively higher prevalence of delayed GE (80% and 75% respectively). In addition, the longer the patient had been in ICU the more normal the rate of GE. Quantification of delayed GE may prove useful by defining patients who may benefit from preventative or therapeutic options. The abnormalities in gastrointestinal motility underlying delayed GE in the critically ill are poorly characterised. Simultaneous manometric and gastric emptying measurements were performed in 15 mechanically ventilated patients and 10 healthy subjects. These studies demonstrated that delayed GE was associated with reduced antral activity, increased pyloric activity and increased retrograde duodenal activity in the patients. Persistent fasting motility during feeding was also frequently observed. Furthermore, the feedback response to small intestinal nutrients was enhanced. This latter observation may provide an explanation for the delayed GE and warrants further investigation. Recent studies suggest that the hormone cholecystokinin may be a mediator of increased small intestinal feedback and, if confirmed, this has clear therapeutic implications. Nutrient absorption has rarely been measured in the critically ill. GE and glucose absorption (using 3-O-methyl glucose) were measured simultaneously in 19 ICU patients and compared to 19 healthy subjects. Glucose absorption was shown to be markedly reduced in the patients. Slow GE was associated with delayed, and reduced, absorption. However, glucose absorption was also reduced in patients with normal GE suggesting that reduced glucose absorption in critical illness is only partly due to delayed GE. Accordingly, measures to improve the effectiveness of GE and thereby improve overall nutritional status may be compromised by abnormal small intestinal absorption. The mechanisms underlying this warrant further investigation. A number of therapeutic options directed at improving the delivery of nutrition were examined. In a study involving 20 mechanically ventilated patients, administration of 200mg erythromycin intravenously was shown to be superior to placebo for treating feed intolerance. The optimal dose of erythromycin, however, was unclear. In a subsequent study involving 35 ICU patients, GE was measured using a breath test technique, before and after 2 different doses of erythromycin or placebo and a ‘low’ intravenous dose (70mg) of erythromycin appeared to be as effective as a ‘moderate’ dose (200mg). Both doses were only effective in subjects who had delayed GE at baseline. Based on the outcome of these studies, low doses of erythromycin have subsequently been routinely used to treat feed intolerance in the critically ill patients at the Royal Adelaide Hospital. Animal and human studies suggested that the antibiotic, cefazolin, may have a prokinetic effect. Cefazolin, however, did not demonstrate similar prokinetic activity at a ‘low’ dose (50mg) in a critically ill cohort. The results of this study do not support the use of this agent, at this dose, as a prokinetic, in this population. If nasogastric administration of nutrition proves unsuccessful an alternative is to infuse nutrient directly into the small intestine. However, the placement of feeding tubes distal to the pylorus is technically difficult. A novel technique for postpyloric tube insertion was examined with promising results. In summary, the studies described in this thesis have provided a number of insights relevant to the management of the critically ill by quantifying the prevalence of feed intolerance and delayed GE, characterising some of the disturbances in gastrointestinal motility underlying this problem, and evaluating a number of therapeutic interventions.<br>Thesis (Ph.D.) -- University of Adelaide, School of Medicine, 2008

Inadequate delivery of nutrition to the critically ill is common, and may adversely affect clinical outcomes, including survival. This thesis reports studies designed to characterise the gastrointestinal dysfunction underlying feed intolerance in the critically ill, as well as the pathophysiology of these dysfunctions, and investigate potential therapeutic measures. While it has been established that enteral nutrition is frequently unsuccessful in the critically ill, assessment of the success of feeding in an Australian intensive care unit (ICU) had not been performed previously. A prospective survey examined the incidence of, and risk factors for, feed intolerance in the ICU at the Royal Adelaide Hospital and demonstrated that, in 40 patients receiving enteral feeding, only about 60% of their nutritional requirements were met at the end of the first week. The main cause for this lack of success was large gastric residual volumes, indicative of delayed gastric emptying (GE). This study, accordingly, quantified the limitations of nutritional delivery in contemporary practice in a local ICU. The results suggest that a better understanding of the pathogenesis underlying this problem is warranted in order to direct research into improved therapies. Scintigraphy is the most accurate technique to measure GE, but is difficult to perform in the ICU. A simpler, more convenient, test would increase the accessibility of GE measurement for both research and clinical purposes. A study comparing a breath test technique and gastric residual volume measurement to the scintigraphic measurement of GE in 25 mechanically ventilated patients demonstrated that GE measured by a breath test technique closely correlated with that measured by scintigraphy. While the breath test had a specificity of 100% it only had a sensitivity of about 60% in the prediction of delayed GE. Similarly, gastric residual volume measurement correlated with scintigraphic measurement of GE but also lacked sensitivity. The breath test has previously been demonstrated to be highly reproducible and it represents a useful option for repeated measurement of GE in the same patient. It is therefore likely to be useful to determine changes in GE over time or in response to a therapeutic intervention. There is a lack of information about the prevalence and determinants of delayed GE in the critically ill. Previous studies have substantial limitations and scintigraphic measurement of GE has only rarely been used. A study comparing GE measured by scintigraphy in 25 patients to 14 healthy subjects demonstrated that GE was delayed in approximately 50% of the ICU patients (>10% retention at 4h) and markedly delayed in about 20% (>50% retention at 4h). Patients with trauma and sepsis appeared to have a relatively higher prevalence of delayed GE (80% and 75% respectively). In addition, the longer the patient had been in ICU the more normal the rate of GE. Quantification of delayed GE may prove useful by defining patients who may benefit from preventative or therapeutic options. The abnormalities in gastrointestinal motility underlying delayed GE in the critically ill are poorly characterised. Simultaneous manometric and gastric emptying measurements were performed in 15 mechanically ventilated patients and 10 healthy subjects. These studies demonstrated that delayed GE was associated with reduced antral activity, increased pyloric activity and increased retrograde duodenal activity in the patients. Persistent fasting motility during feeding was also frequently observed. Furthermore, the feedback response to small intestinal nutrients was enhanced. This latter observation may provide an explanation for the delayed GE and warrants further investigation. Recent studies suggest that the hormone cholecystokinin may be a mediator of increased small intestinal feedback and, if confirmed, this has clear therapeutic implications. Nutrient absorption has rarely been measured in the critically ill. GE and glucose absorption (using 3-O-methyl glucose) were measured simultaneously in 19 ICU patients and compared to 19 healthy subjects. Glucose absorption was shown to be markedly reduced in the patients. Slow GE was associated with delayed, and reduced, absorption. However, glucose absorption was also reduced in patients with normal GE suggesting that reduced glucose absorption in critical illness is only partly due to delayed GE. Accordingly, measures to improve the effectiveness of GE and thereby improve overall nutritional status may be compromised by abnormal small intestinal absorption. The mechanisms underlying this warrant further investigation. A number of therapeutic options directed at improving the delivery of nutrition were examined. In a study involving 20 mechanically ventilated patients, administration of 200mg erythromycin intravenously was shown to be superior to placebo for treating feed intolerance. The optimal dose of erythromycin, however, was unclear. In a subsequent study involving 35 ICU patients, GE was measured using a breath test technique, before and after 2 different doses of erythromycin or placebo and a ‘low’ intravenous dose (70mg) of erythromycin appeared to be as effective as a ‘moderate’ dose (200mg). Both doses were only effective in subjects who had delayed GE at baseline. Based on the outcome of these studies, low doses of erythromycin have subsequently been routinely used to treat feed intolerance in the critically ill patients at the Royal Adelaide Hospital. Animal and human studies suggested that the antibiotic, cefazolin, may have a prokinetic effect. Cefazolin, however, did not demonstrate similar prokinetic activity at a ‘low’ dose (50mg) in a critically ill cohort. The results of this study do not support the use of this agent, at this dose, as a prokinetic, in this population. If nasogastric administration of nutrition proves unsuccessful an alternative is to infuse nutrient directly into the small intestine. However, the placement of feeding tubes distal to the pylorus is technically difficult. A novel technique for postpyloric tube insertion was examined with promising results. In summary, the studies described in this thesis have provided a number of insights relevant to the management of the critically ill by quantifying the prevalence of feed intolerance and delayed GE, characterising some of the disturbances in gastrointestinal motility underlying this problem, and evaluating a number of therapeutic interventions.<br>http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1345143<br>Thesis (Ph.D.) -- University of Adelaide, School of Medicine, 2008

Bibliography: leaves 258-294.<br>xv, 294 leaves : ill. (1 col.) ; 30 cm.<br>Title page, contents and abstract only. The complete thesis in print form is available from the University Library.<br>Examines the organisation and control of the antropyloroduodenal motor unit in both healthy human volunteers and patients with gastroparesis.<br>Thesis (Ph.D.)--University of Adelaide, Dept. of Medicine, 1992

Transpyloric flow is the final step in gastric emptying prior to intestinal absorption of nutrients and medications. The details of this process are still incompletely understood. Transpyloric flow is bi-directional, contrasting with the general perception of solely forward flow implied by studies of gross gastric emptying. The degree to which the patterns of bi-directional transpyloric flow reflect emptying of meals of varied physicochemical composition, its mechanical determinants and effect on delivery of oral medications have been evaluated by the studies presented in this thesis.

In an irritable bowel syndrome (IBS) rat model, S. chinensis reversed the exaggerated visceral nocicptive responses (judged by abdominal withdrawal reflex and electromyographic measurement) to colorectal distension induced by neonatal maternal separation. Relief of visceral hypersensitivity by S. chinensis could be related to the decrease of elevated 5-HT level and the reduction in 5-HT3 receptor expression in colon.<br>In summary, given the modulatory effects on intestinal motility and visceral sensation, Schisandra chinensis would be potentially useful for the treatment of relieving diarrhea and visceral pain symptoms in IBS patients. Schisandra lignans, the major absorbable components, can be regarded as the active ingredients in S. chinensis for the potential treatment of IBS.<br>Schisandra chinensis, which is named "Wu-Wei-Zi" in Chinese Pin Yin, is widely used in Chinese medicine as an astringent, tonic and sedative agent. Dibenzo[a,c]-cyclooctadiene lignans are the major components of this herb. In the present study, the chemical constituents of S. chinensis were first characterized. A HPLC-DAD method was developed and validated for quantitative analysis of four major Schisandra lignans, namely, schisandrin (SCH-1), gomisin A (SCH-2), deoxyschisandrin (SCH-3) and gamma-schisandrin (SCH-4), in the aqueous and ethanolic extracts of S. chinensis. The ethanolic extract contains higher amount of lignan components than aqueous extract. The HPLC method has also been employed to obtain chromatographic fingerprintings to distinguish S. chinensis from a related species, S. sphenanthera.<br>The modulatory effects of both S. chinensis extracts and four major lignans on intestinal motility were evaluated using in vitro intestinal motility assays. The tested compounds induced relaxation on guinea pig ileum contracted by acetylcholine, serotonin and electrical field stimulation, as well as on rat colon with spontaneous contractility. While SCH-3 was most potent in inhibiting sensorimotor response in guinea pig ileum, SCH-1 displayed the highest potency of inhibition on spontaneous contraction of rat colon.<br>The relaxant effect on rat colon induced by SCH-1 has been demonstrated to involve two or more non-adrenergic non-cholinergic mediators. Nitric oxide was likely to be one of the inhibitory transmitters that involved cGMP-dependent pathways, whereas the non-nitrergic component was apamin-sensitive, but probably excluded vasoactive intestinal peptide (VIP) and adenosine.<br>With the aid of HPLC-DAD-MS for qualitative and quantitative analyses, the absorption of S. chinensis in the rat everted gut sac and human Caco-2 monolayer in vitro models have been profiled. Fifteen Schisandra lignans were identified as the major absorbable components of S. chinensis in these models. Transport study on SCH-1 has shown a passive diffusion pathway with high permeability. In an in vivo study, metabolites of Schisandra lignans could be found in rat plasma after a single oral administration of S. chinensis extract. The plasma pharmacokinetics of S. chinensis in rats was further evaluated using simultaneous quantification of four representative Schisandra lignans (SCH-1, SCH-2, SCH-3 and SCH-4).<br>Yang, Jiaming.<br>Adviser: Chun-Tao Che.<br>Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: .<br>Thesis (Ph.D.)--Chinese University of Hong Kong, 2009.<br>Includes bibliographical references (leaves 262-283).<br>Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.<br>Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.<br>Abstract also in Chinese.

Wang, Hui Chuan.<br>Thesis (Ph.D.)--Chinese University of Hong Kong, 2013.<br>Includes bibliographical references (leaves 184-202).<br>Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.<br>Abstract also in Chinese.

Indiana University-Purdue University Indianapolis (IUPUI)<br>Gastric residual volume (GRV) is a clinical assessment to evaluate gastric emptying and enteral feeding tolerance. Factors such as the tube size, tube material, tube port configuration, placement of the tube in the gastric fluid, the amount of fluid and person completing the assessment may influence the accuracy of residual volume assessment. Little attention has been paid to assessing the accuracy of GRV measurement when the actual volume being aspirated is known, and no studies have compared the accuracy in obtaining RV using the three different techniques reported in the literature that are used to obtain aspirate in practice (syringe, suction, and gravity drainage). This in vitro study evaluated three different methods for aspirating feeding formula through two different tube sizes (10 Fr [small] and 18 Fr [large]), tube materials (polyvinyl chloride and polyurethane), using four levels of nursing experience (student, novice, experienced and expert) blinded to the five fixed fluid volumes of feeding formula in a simulated stomach, to determine if the RV can be accurately obtained. The study design consisted of a 3x2x2x4x5 completely randomized factorial ANOVA (with a total of 240 cells) and 479 RV assessments were made by the four nurse participants. All three methods (syringe, suction and gravity) used to aspirate RV did not perform substantially well in aspirating fluid, and on average, the methods were able to aspirate about 50% of the volume available. The syringe and suction techniques were comparable and produced higher proportions of RVs, although the interrater reliability of RV assessment was better with the syringe method. The gravity technique generally performed poorly. Overall, the polyvinyl chloride material and smaller tubes were associated with higher RV assessments. RV assessment is a variable assessment and the three methods did not perform well in this in vitro study. These findings should be further explored and confirmed using larger samples. This knowledge will be important in establishing the best technique for assessing RV to maximize EN delivery in practice and will contribute to future research to test strategies to optimize EN intake in critically ill patients.